Microporous and mesoporous materials, such as zeolites, activated carbon, silica and metal organic frameworks (MOFs) are widely used in heterogeneous catalysis, gas storage, adsorption and separations. It is hoped that recent development of polymer-based microporous materials may provide new opportunities in hydrogen storage and heterogeneous catalysis, since organic materials have certain advantages over other materials. Microporous polymeric materials may have unique surface properties that can be tailored to facilitate chemoselective adsorption, separation and catalysis. Although hard and soft templates have been widely used in the preparation of porous materials, a bottom-up approach allows for the synthesis of porous materials with tailored porous structure and surface chemistry. However, robust microporous and mesoporous polymers synthesized from molecular building blocks are still rather limited. Recently, polymers with intrinsic microporosity (PIMs) have been prepared entirely of fused-ring subunits to provide a rigid nonplanar block or a spiro-center for the contortion of macromolecular structure with the inefficient space packing model. Hypercrosslinked polymers represent another class of predominantly microporous polymers. Similar to PIMs, the porosity of hypercrosslinked material is a result of extensive crosslinking that make polymer chains pack inefficiently and prevent the formation of dense and non-porous systems. Generally, the porosity of these two types of materials is created by incorporating rigid units in the polymer network. Yaghi's group developed covalent organic frameworks (COFs) that are composed fully of rigid network without any “soft” knots (A. P. Cote, A. I. Benin, N. W. Ockwig, M. O'Keefe, A. J. Matzger, O. M. Yaghi, Science 2005, 310, 1166; H. M. El-Kaderi, J. R. Hunt, J. L. Mendoza-Cortes, A. P. Cote, R. E. Taylor, M. O'Keefe, O. M. Yaghi, Science 2007, 316, 268). These novel materials are constructed by dehydration condensation reaction of boronic acids. Due to the kinetic reversibility and quasi-inorganic nature of the reaction, highly crystalline products are attained.
There is a need for a polymer having intrinsic microporosity which is relatively simple to synthesise and is made from relatively readily available starting materials. It would be preferred if the microporosity were controllable.